When telling calibre to download metadata for a single book, it usually comes up with a list of options, and you choose which you think is best.

When doing a bulk fetch of metadata it decides itself which one is the best - how does it pick?

The reason I ask is because before I let it go through and fetch it for my whole collection I decided to do a dry run on just a couple of books, choosing the first two Jim Butcher books - Storm Front and Fool Moon.

Storm front appeared to have picked a reasonably sensible option, though it changes the title from just "Storm Front" to "Storm Front (The Dresden Files, Book 1)"
Fool Moon, however, is a different story, for some reason it picked "Luna Llena / Fool Moon (The Dresden Files) (Spanish Edition)" and added an extra author (translator).

Any thoughts on why it picked that one, and how to get round it in a bulk fetch would be much appreciated.